Directional lamp types, including PAR, R, BR, and MR, are available with different beam spread specifications. A typical lamp of this type only provides a fixed beam spread that is not selectable by the end user. In order to have a different beam spread, a different lamp with a different spread specification is needed.
The beam spread desired for a particular lighting task can be used to determine the lamp selection. For example, a spotlight produces a narrow beam of intense light that can be used for display lighting, a floodlight produces a broader beam suitable for general lighting tasks, and a wallwasher produces an even broader beam that can light entire wall surfaces in architectural spaces.
Mechanically actuated, variable optics can provide adjustment of the beam spread emitted from a fixture by changing the shape of optical surfaces (e.g., reflecting and/or refracting surfaces) and deforming the lens surface. Such mechanical actuation can change the beam spread emitted from a fixture without changing the lamp installed in the fixture.